Using the X-24 flash with a T3greenspun.com : LUSENET : Konica 35mm SLRs : One Thread
I have a X-24 Konica flash to couples up with Konica slrs such as the FS-1 and FT-1 and becomes a dedicated flash for them. I would like to use it with my T3. My understanding is that for the auto feature to be used I have to set the flash to the green or orange setting. If I choose the green mark, then with 100 ASA film I have to set the lense aperature to f 2.8, while for 400 ASA film I must choose f 5.6. However, I will be using ASA 200 film. Am I correct in assuming that I then must set the aperature at f 4 as the proper setting for the green auto position? I've been testing this with a flash meter and for some reason the reading for the flash output is closer to f 2.8 than 4? I wonder why? Anybody have an answer or suggestion? Thanks.
-- Anonymous, May 19, 2000
I have done similar experiments with my X24 and a flash meter and come to the same conclusions. If used on a non-dedicated camera, the auto sensor mechanism in the X24 seems to default to ASA 400 film. Therefore, the appropriate f stop to use in the green mode would be f5.6 (400 ASA), f4.0 (200 ASA) and f2.8 (100 ASA). The orange settings for auto use should be f11.0 (400 ASA), f8.0 (200 ASA) and f5.6 (100 ASA).
The light output as measured by your flash meter could be off for a couple of reasons. A likely problem is as follows. In the auto mode, the sensor in the flash cuts off the light output when the amount of light reflected back reaches the target. If you have your flash meter set up against a background that reflects more or less light than average (i.e. 18% grey card) the flash sensor will be "fooled". If, for instance, the flash meter was set against a white wall, the flash sensor will receive a lot of reflected light back, and will quickly quench the light output. This will show up on the flash meter as little light received, and a wider f stop required (in other words, the flash meter didn't receive much light, so it would suggest you open up to f2.8 or lower instead of the f4.0 above).
In playing with the flash and meter, you will probably find that the measured light output changes quite a bit as you move the flash (therefore the sensor) even slightly off axis from the meter. My own experiments also indicate that many flashes don't seem to measure out to quite the same light output that is advertised - or that they have a "hot spot" that is close will lots of light falloff outside of it. You can switch your flash to manual and measure output with your flash meter to check the guide number - should be 80 for the X24 with 100 ASA.
I think the best thing to do is use the above as a starting point (f4.0 with 200 ASA) and then adjust the auto fstop, if required, when you get your film back. Modern films seem to have enough exposure latitude that they can handle even significant over or under exposure and still produce a pretty good photo ...
-- Anonymous, May 19, 2000